Micrometer plug gauge



Oct. 24, 1944. yous I 2,361,336

" MIGROMETER PLUG GAUGE Filed Oct. '6, 1943 FIGJ.

INVENTOR. HARRY evous I ATTORNEYS Patented Oct. 24, 1944 UNITED STATES PATENT, OFFICE I 2,361,336 Q MICBOMETE-R PLUG GAUGE.

7 Harry G. Volis, Detroit, I I Application Octoberli, 1943, Serial No. 505,117 v 2 Claims. (01. 33-178) The present invention relates to plug gauges and specifically to plug gauges having .micrometric adjustment whereby to vary the size and obtain accurate measurement of bores.

Among the objects of the invention is agauge of the type indicated which is greatly simplified and more rugged in construction, and which is easy to manufacture and assemble.

Other objects and advantages will be apparent to those skilled in the art upon reference to the following description and the accompanying drawing in which Figure 1 is a view in elevation of the gauge.

Figure 2 is a central longitudinal section thereof.

Figure 3 is an end view.

I Figure 4 is a section on line 4-4 of Figure 2.

Figure 5 is an exploded view of a portion of the gauge, inverted for clarity.

As shown in the drawing, the gauge consists of a body portion containing a plurality of blades movable radially through the action 'of a cam carrying rod. The latter is in turn movable 1ongitudinally through the action of a screw as in the conventional micrometer, the number of turns or portions of turns being determined by means of a suitable graduated scale.

In the drawing. the embodiment illustrate comprises a body II] made up of two portions II and I2 which are substantially identical except that portion I2 is provided with an axial boss |2A threaded on the outside as at I2B, while the other portion I I is flat on the corresponding surface. A further difference is in the axial opening as will appear later.

The portion II is shown in perspective in Fig. 5 and consists of a cup having a plurality of slots I5 which pass through the cup walls and are continuations of grooves I5A cut in the bottom of the cup and extending radially from the central opening Hi. There are also a plurality of axially extending openings I8 through the cup bottom, through which extend suitable screws adapted to hold the body parts in assembled relation.

In each of the slots |5|5A is a blade 20 provided at one end with an inclined surface 20A and in one lateral edge a narrow slot 203 adapted to receive a flat spring 2 I.

The blades 20 extend from the bottoms of the slots to the top edge of the cup, being substantially flush therewith, while the spring 2| is arranged with its free ends against the inside surface of the cup wall as shown best in Figure 4. Further, the blades 20 are sufficiently long to have the inclined end 20A extend into the central opening I6 when the outer end is flush with the outside wall of the cup.

Mounted to slide longitudinally in the central opening I6 is a rod 25 having formed thereon the conical cams 26 adapted to coact with blade surfaces 20A to move the blades radially of the cup against the action of springs 2 I As shown best in Figure 2, the body Ill is preferably made of two portions II and I2, the portion having just been described. The portion I2, insofar as the cup portion is concerned, is the same as portion II, having slots similar to slots |5|5A and containing identical blades 20 and springs 2|. The central opening 36, however, is somewhat different. It is of the same size as opening I6 fora part of its length, but is smaller where it extends through the threaded boss IZA. This latter portion is preferably of such size as to make an accurate sliding fit with the rod 25.

In assembling the parts so far described, the rod 25 is first passed through the portion I2 and then'the blades 20 and springs 2| installed therein. Over the cup portion 'of the portion I2 is thenplaced the flat side of portion II to act as a cover. After the blades 20 and springs 2| have been assembled in portion II, a cover plate 40 is applied to the cup of the latter and the screws I'I used to hold the assembly together, these screws passing through the cover plate 4|], the portion II and threaded into the portion I2.

As shown in Fig. 2, the rod 25 extends beyond the part I2 and is flattened on the end and is enclosed in a suitable tube threaded on the boss I2A. The outer end of tube 45 is closed except for a threaded axial opening 45A and is reduced somewhat in diameter as at 45B, being provided with suitable graduations 45C.

Threaded into the opening 45A is a short rod 46 which extends into tube 45 a suificient distance to coact with rod 25, being preferably cupped-at its end to retain a steel .ball 41 which contacts the rod 25 and permits the exertion of thrust upon the latter with a minimum of friction.

Upon the outerend of rod 45 is fixed a thimble 50, a suitable set screw 5| being used. This thimble 50 is provided with a beveled surface 52 suitably graduated as shown, so that the number of turns of the thimble and thereby the rod 46 ma be ascertained, as is conventional in micrometers. The tube 45 and thimble 5|] are preferably knurled as shown in Figure 1.

It should be noted that while the gauge is shown as consisting of the two sections II and I2 and each with four blades 20, it is obvious that the relatively thin walled cup-shaped body having radial grooves in the inner surface of the cap bottom and slots in the wall of said cup, said slots being continuous with and equal in width with said grooves, blades in said grooves and slots, a transversely arranged flat spring carried by each of said blades and having its free ends'acting against the inner surface of said body and tending to move said blades radially inward, means to move said blades radially outward, and means to indicate the amount of such outward movement.

2. A micrometer plug gauge consisting of a relatively thin walled cup shaped body having radial grooves in the inner surface of the cup bottom and slots in the wall of said cup, said slots being continuous with and equal in width with said grooves, blades in said grooves and slots,

spring means tending to move said blades radially inward, a cam on the inner end of each blade, an axially located longitudinally movable rod provided with a cam'adapted to coact with the blade cam to move said blades radially outward upon longitudinal movement of said rod and means to indicate the amount of such movement.

HARRY G. VOLIS. 

